scholarly journals Rate of change of the pulsation periods in the PG 1159 star PG 0122+200

2008 ◽  
Vol 4 (S252) ◽  
pp. 157-162
Author(s):  
G. Vauclair ◽  
J.-N. Fu ◽  
J.-E. Solheim ◽  
S.-L. Kim ◽  
M. Chevreton ◽  
...  
Keyword(s):  
White Dwarf ◽  
Rapid Evolution ◽  
Theoretical Models ◽  
Variable Stars ◽  
Rate Of Change ◽  
Point Of View ◽  
Short Time Scale ◽  
Theoretical Point ◽  
Instability Strip ◽  
Core Cooling

AbstractThe pre-white dwarf pulsators of PG 1159 type, or GW Virginis variable stars, are in a phase of rapid evolution towards the white dwarf cooling sequence. The rate of change of their nonradial g-mode frequencies can be measured on a reasonably short time scale. From a theoretical point of view, it was expected that one could derive the rate of cooling of the stellar core from such measurements. At the cool end of the GW Virginis instability strip, it is predicted that the neutrinos flux dominates the cooling. PG 0122+200 which defines the red edge of the instability strip is in principle a good candidate to check this prediction. It has been followed-up through multisite photometric campaigns for about fifteen years. We report here the first determination of the rate of change of its 7 largest amplitude frequencies. We find that the amplitudes of the frequency variations are one to two orders of magnitude larger than predicted by theoretical models based on the assumption that these variations are uniquely caused by cooling. The time scales of the variations are much shorter than the ones expected from a neutrino dominated core cooling. These results point to the existence of other mechanisms responsible for the frequency variability. We discuss the role of nonlinearities as one possible mechanism.

scholarly journals La poética del urbanismo de Le Corbusier: arte y función en la ciudad moderna

2015 ◽  
Author(s):  
Emanoela Gehlen Bregolin ◽  
Andrea Soler Machado
Keyword(s):  
Urban Planning ◽  
Theoretical Models ◽  
Le Corbusier ◽  
Point Of View ◽  
Theoretical Point ◽  
Palabras Clave ◽  
América Del Sur ◽  
And Function ◽  
Historical Moment ◽  
The City

Resumen: El objetivo de este artículo es demostrar que existe una poética en el urbanismo de Le Corbusier y que el tema se mantiene y se transforma en sus modelos teóricos y sus derivaciones. Desde el punto de vista teórico-metodológico, parte-se del presupuesto de que esa poética es el resultado de la dualidad entre arte y función presente en su pensamiento, originada en su formación personal y el momento histórico en el que produce su obra. El analisis se estructura con la agrupación de su produción urbanística en cuatro fases: 1-los años 1920: el Plan Ideal; 2-1929-38: las ciudades de América del sur y los viaductos; 3-1930-50: la Ville Radieuse; 4-Después de la Segunda Guerra Mundial: la ciudad de los 7V y la Unité d’habitation. La reflexión final retoma la visión general de su produción urbanística y la vincula al concepto de utopia. Abstract: The goal of this article is to demonstrate that there is an aspect of poetics in Le Corbusier’s urbanism and that this theme is maintained and you can see it being transformed through the theoretical models and its derivations. From the methodological and theoretical point of view, we make the assumption that the poetics is the result of the duality between art and function present in his thought, which comes from the historical moment in which his work was made and from his personal background. This analysis is structured by grouping his urban planning works in for phases; the 1920s: the Ideal City; 1929-38: the cities of South America and the viaduct; 1930-50: the Ville Radieuse; after the II World War: the city of 7V and the Unité d’habitation. The final considerations bring back the general vision of his urban planning works and tie it to the concept of utopia.  Palabras clave: Le Corbusier; Urbanismo; Poética; Arte; Función. Keywords: Le Corbusier; Urbanism; Poetics; Art; Función. DOI: http://dx.doi.org/10.4995/LC2015.2015.1545

scholarly journals Luminosity Calibrations with Hipparcos: Theoretical Point of View

2002 ◽  
Vol 12 ◽  
pp. 669-672
Author(s):  
Yveline Lebreton
Keyword(s):  
Chemical Composition ◽  
Theoretical Models ◽  
Calibration Procedure ◽  
Point Of View ◽  
Chemical Compositions ◽  
Theoretical Point ◽  
Observational Material ◽  
Stellar Models ◽  
Stellar Temperatures

AbstractHipparcos provided us with valuable observational material that can be used to anchor more firmly the Galactic and extragalactic distance scales. A calibration which is applicable to all stars must allow for differences in chemical composition and other properties, which may require the use of theoretical models. I discuss some difficulties encountered in the calibration procedure that are related (1) to the determinations of stellar temperatures, luminosities and chemical compositions, (2) to remaining weaknesses of theoretical stellar models, and (3) to the transformations of the model outputs from the (Mbol,Teff) plane into any colour-magnitude or colour-colour diagram.

scholarly journals Introduction

1993 ◽  
Vol 134 ◽  
pp. 1-5
Author(s):  
M. Takeuti
Keyword(s):  
Nonlinear Theory ◽  
Variable Stars ◽  
Point Of View ◽  
Theoretical Point ◽  
Stellar Pulsation ◽  
Hydrodynamic Study ◽  
The Impact ◽  
Historical Sketch

AbstractA historical sketch of the nonlinear theory of variable stars is outlined briefly. The main break-through came from the hydrodynamic study of stellar pulsation. From a theoretical point of view, coupling needs to be discussed more carefully. The impact of new opacities on the astrophysical problems is also discussed.

MIGRATION AS A MECHANISM TO PROMOTE COOPERATION

2008 ◽  
Vol 11 (04) ◽  
pp. 641-652 ◽  
Author(s):  
DIRK HELBING ◽  
WENJIAN YU
Keyword(s):  
Theoretical Models ◽  
Theoretical Explanation ◽  
Point Of View ◽  
Spatiotemporal Pattern ◽  
Theoretical Point ◽  
Strategic Interactions ◽  
Directed Motion ◽  
Social Attraction ◽  
Configurational Analysis ◽  
Spatial Games

A unified approach is proposed, which integrates game-theoretical models with models of directed motion. Specifically, strategic interactions in space and imitation of more successful neighboring strategies, as studied by spatial games, are combined with success-driven migration based on "test interactions" or wealth-related "neighborhood tagging." It turns out that such directed migration allows cooperators to evade defectors and (in constrast to purely diffusive motion) also to find other cooperators in order to form clusters ("islands of cooperation"). This can increase the cooperation to a great extent. Moreover, success-driven motion leads to interesting spatiotemporal pattern-formation phenomena, which are clearly different from those produced by previously studied spatial games. Despite the simplicity of the model, the forming patterns appear to realistically represent many stylized facts of social interactions, particularly phenomena such as social networking, urban aggregation, social segregation or turn-taking. Furthermore, migration games offer a game-theoretical explanation of social attraction and repulsion, based on payoff-related mobility, and they display a larger variety than conventional games, as their behavior is not invariant to shifting all payoffs by a constant amount. In summary, the combination of strategic interactions and imitation with models of directed motion has high potential for understanding empirical observations in the social, biological and economic sciences from a game-theoretical point of view. Finally, the breakdown of cooperation in the prisoner's dilemma at high values of temptation is explained by configurational analysis.

scholarly journals Theory of Evolution of the Central Star

1978 ◽  
Vol 76 ◽  
pp. 195-199
Author(s):  
Giora Shaviv
Keyword(s):  
White Dwarf ◽  
Planetary Nebulae ◽  
Central Star ◽  
Point Of View ◽  
Linear Size ◽  
Theoretical Point ◽  
Fundamental Feature ◽  
Theory Of Evolution ◽  
The Core ◽  
Hr Diagram

The fundamental feature of the evolution of the central star of planetary nebulae (CPN) is the cooling of the core towards a white dwarf. The basic observations were made by O'Dell (1963), Seaton (1966), and Harman and Seaton (1964); namely, they discovered a correlation between the linear size of the nebula and the position of the CNP in the HR diagram. Typical values for the velocity of expansion are 10–30 km/sec and the largest size observed for a nebula is ∼0.6 pc and hence the lifetime is 2–6 × 104 years. From a theoretical point of view the important fact about the Harman-Seaton sequence (HS) is the implication on the evolution of the central star. The star first heats up, L and Te increase, then L decreases. But Te keeps increasing until finally Te decreases also (shown schematically in Figure 2). Thus the HS is an evolutionary sequence and not a locus of stars.

scholarly journals Moving Through The Instability Strip

1993 ◽  
Vol 139 ◽  
pp. 419-419
Author(s):  
Emilia Pisani Belserene
Keyword(s):  
Rate Of Change ◽  
Point Of View ◽  
Instability Strip ◽  
Rr Lyrae Stars ◽  
Sigma Level ◽  
Rr Lyrae ◽  
Linear Fit ◽  
Lyrae Stars ◽  
Student Assistants ◽  
Better Than

The purpose: To look at period changes in pulsating variables from the point of view of stellar evolution. Is there evidence of systematic, slow changes that might be caused by the changes in mean density during passage across the Instability Strip?The data: O – C diagrams for 67 RR Lyrae stars and Cepheids by student assistants at the Maria Mitchell Observatory, and for 88 northern Cepheids by L. SzabadosThe method: Least-squares lines and parabolae (unless the O – C diagram shows that the period has changed in both directions). The rate of change of period comes from the coefficient of the square term in the parabola. The principal feature of these analyses is that the rate is taken to be non-zero only if the parabola is significantly better than the linear fit, at the 2-sigma level.

Timber Auctions in the Context of the Modern Auction Theory

2007 ◽  
pp. 86-94
Author(s):  
A. Manakov
Keyword(s):  
Theoretical Analysis ◽  
Auction Theory ◽  
Point Of View ◽  
Theoretical Point ◽  
English Auction ◽  
Analysis And Evaluation

The article provides theoretical analysis and evaluation of the timber auctions reforms in Russia. The author shows that the mechanism of the "combined auctions", which functioned until recently, is more appropriate from the theoretical point of view (and from the point of view of the Russian practice) as compared to the officially approved format of the English auction.

A novel cryptosystem based on abstract automata and Latin cubes

2015 ◽  
Vol 52 (2) ◽  
pp. 221-232
Author(s):  
Pál Dömösi ◽  
Géza Horváth
Keyword(s):  
Block Cipher ◽  
Finite Automata ◽  
Theoretical Background ◽  
Point Of View ◽  
Theoretical Point ◽  
Transition Matrices ◽  
Encryption And Decryption ◽  
Secret Keys ◽  
Automata Network ◽  
Fully Functioning

In this paper we introduce a novel block cipher based on the composition of abstract finite automata and Latin cubes. For information encryption and decryption the apparatus uses the same secret keys, which consist of key-automata based on composition of abstract finite automata such that the transition matrices of the component automata form Latin cubes. The aim of the paper is to show the essence of our algorithms not only for specialists working in compositions of abstract automata but also for all researchers interested in cryptosystems. Therefore, automata theoretical background of our results is not emphasized. The introduced cryptosystem is important also from a theoretical point of view, because it is the first fully functioning block cipher based on automata network.

Graffiti als Version und Subversion–Praxen kultureller Re-Regulierung und die Möglichkeit von Gratiforschung

2010 ◽  
Vol 55 (2) ◽  
pp. 11-25 ◽  
Author(s):  
Bernd Dollinger
Keyword(s):  
Social Life ◽  
Point Of View ◽  
Theoretical Point ◽  
Research Practice ◽  
Wird Eine ◽  
Multiple Perspectives

Der Beitrag geht von Versuchen aus, integrative Perspektiven einer überaus heterogenen Graffitiforschung zu bestimmen. In Auseinandersetzung insbesondere mit Bruno Latours Ansatz des »Iconoclash« wird eine kulturtheoretische Referenz bestimmt, die Graffiti als Version identifiziert, d. h. als semiotisch orientierte Veränderung räumlich situierter Ordnungs- und Regulierungspraxen. Ihnen kann, wenn auch nicht zwingend, eine subversive Qualität zukommen. Durch die Ausrichtung am Konzept einer Version wird beansprucht, Forderungen einer normativ weitgehend abstinenten, nicht-essentialistischen und für komplexe Fragen der Identitäts- und Raumpolitik offenen Forschungspraxis einzulösen.<br><br>The contribution attempts to integrate multiple perspectives of current largely heterogeneous graffiti scholarship. Referring to Bruno Latour’s concept »iconoclash«, we discuss graffiti from a cultural-theoretical point of view as a »version«. It appears as a semiotically oriented modification of spatially situated practices that regulate social life. Often, but not necessarily, these practices involve subversive qualities. The concept of »version« facilitates a non-normative and non-essentialist strategy of research. This enables an explorative research practice in which the complex matters of identity and space politics that are associated with graffiti can be addressed.

scholarly journals How Digital Inclusion Increase Opportunities for Young People: Case of NEETs from Bulgaria, Romania and Turkey

2021 ◽  
Vol 13 (14) ◽  
pp. 7894
Author(s):  
Gabriela Neagu ◽  
Muhammet Berigel ◽  
Vladislava Lendzhova
Keyword(s):  
Data Analysis ◽  
Rural Areas ◽  
Secondary Data ◽  
Point Of View ◽  
Multidimensional Analysis ◽  
Theoretical Point ◽  
Digital Inclusion ◽  
Virtual Mobility ◽  
Alternative Research ◽  
High Share

This paper examines the perspectives of rural NEETs in the information society. Our analysis focuses on the situation of three European countries—Bulgaria, Romania, and Turkey—characterized by a high share of rural areas and a population of NEETs. From a methodological point of view, we use alternative research methods (secondary data analysis) with statistical methods (simple linear regression). From a theoretical point of view, we will opt for a multidimensional analysis perspective: the theory of digital divide, digital inclusion, virtual mobility, etc. Through data analysis, we expect to obtain a more complete and detailed picture of the ICT situation in rural areas (level of digital skills, level of digital inclusion) to demonstrate the importance of ICT in optimizing virtual mobility for the living conditions of the population, especially the NEET population.

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